Four African girls just showed off a urine-powered generator at Maker Faire Africa, in Lagos. Duro-Aina Adebola, Akindele Abiola and Faleke Oluwatoyin, 14, and Bello Eniola, 15, built the device, which uses an electrolytic cell to separate hydrogen out of urine, Maker Faire's website explained.

The hydrogen goes into a water filter for purification, which then gets pushed into the gas cylinder. The gas cylinder pushes hydrogen into a cylinder of liquid borax, which is used to remove the moisture from the hydrogen gas. This purified hydrogen gas is pushed into the generator.

A liter of urine generates six hours of electricity.

While the system does have one-way valves for safety, more robust measures may be needed before commercialization.

As the writeup noted, "let's be honest that this is something of an explosive device."